Swash-plate drag bearing

ABSTRACT

An arc-shaped rolling bearing segment ( 14 ) comprising a cage ( 16 ) and rolling elements ( 15 ) for a swash plate pivoting bearing of a hydraulic axial piston machine is characterized in that the cage ( 16 ) and the support peg ( 17 ) are made as a single piece out of a polymer material, and the support peg ( 17 ) is surrounded, at least over a part of its axial length, by a metal ring ( 18 ).

FIELD OF THE INVENTION

The invention concerns a swash plate pivoting bearing for a hydraulicaxial piston machine in which rolling bearing segments are arrangedbetween a hollow cylindrical bearing surface for the swash plate in ahousing and a cylindrical bearing surface on the swash plate, whichrolling bearing segments are retained in arc-shaped cages that areconfigured as solid cages and comprise a support peg for re-positioningthe cage upon displacement from a desired position, said support pegextending parallel to the rolling element pockets and projecting beyondthe cage width while being connected to a readjusting device.

BACKGROUND OF THE INVENTION

In this known type of structure, a readjusting device associated to theswash plate pivoting bearing prevents the cage that receives the rollingbearing elements from slipping out of its predetermined region ofmovement, namely its favorable position in the pivoting bearing. In theabsence of a readjusting device such slipping is possible because therolling bearing elements not only execute rolling movements but alsosliding movements due to rapid pivoting and/or vibrations and/or themass inertia of the rolling bearing segment that lead to a positionaldisplacement of the rolling element segment. This results in anunfavorable position of the retaining segment or segments relative tothe direction of load.

Such swash plate pivoting bearings with different types of readjustingdevices are described, for example, in DE-OS 28 26 928, DE-AS 25 21 312or EP 01 82 354 B1. These readjusting devices require a point ofarticulation on the arc-shaped cage. From DE-GM 87 10 514, it is knownin this connection to provide a bore in the cage and insert a metal pininto this bore which is then in contact with the readjusting device. Adrawback of such arrangements is that in cage segments of small radialoverall dimensions, this pin cannot be accommodated in the cage for lackof space.

SUMMARY OF THE INVENTION

The object of the invention is therefore to provide an improved cage ofthe pre-cited type in which, with the help of simple measures, thesupport peg can be arranged securely, reliably, and inexpensively on thecage, and the occurring restoring forces do not cause a wear of thecage.

The invention achieves this object by the fact that the cage and thesupport peg are made as a single piece out of a polymer material, andthe support peg is surrounded, at least over a part of its axial length,by a metal ring.

By the configuration of the arc-shaped cage according to the inventionit is assured that one-piece cages including the actual cage segment andthe support peg can be produced without any problem in any desired sizeand dimensions. The metal ring connected to the support peg assures onthe one hand that the cage segment has an adequate resistance to thecontact pressure at its point of contact with the readjusting deviceand, on the other hand, that an adequate wear resistance to the slidingmotion between the support peg and the readjusting device is created.Thus, the metal ring serves as a wear protector because, upon a directcontact of the support peg with the readjusting device, a considerablewear of the polymer material would take place at the point of contact.In addition, compared to the polymer material, the metal ring has aconsiderably higher permissible surface pressure.

Advantageous embodiments of the invention are described as follows. Themetal ring is made of a steel material and subjected to a heattreatment. With this heat treatment, the steel material can be endowedwith substantially higher strength values. The metal ring can comprise aprojection on its inner peripheral surface and the metal ring cancomprise a projection on its inner peripheral surface and the positiveengagement thus formed creates an inseparable connection between thesupport peg and the metal ring. The metal ring may comprise a depressionat least on a part of its periphery which radially inward orienteddepression assures on the one side, as described above, that a positiveconnection is formed between the support peg and the metal ring, and onthe other side, that the readjusting device can be reliably guided inthe depression on the outer peripheral surface of the metal ring.Finally, the metal ring is sprayed over on its inner end face with cagematerial.

The invention will now be described more closely with reference to thefollowing examples of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a radial section through an arc-shaped rolling bearingsegment,

FIG. 2 shows a section taken along ling II—II of FIG. 1,

FIGS. 3, 4 and 5 are enlarged representations of the detail Z of FIG. 2,

FIG. 6 shows a longitudinal section through a hydraulic axial pistonmachine.

DETAILED DESCRIPTION OF THE DRAWINGS

As can be seen in FIG. 6, the axial piston machine comprises acylindrical drum 1 that is arranged on a shaft 2 which can be a drivingor a driven shaft depending on whether the machine is used as a pump ora motor. The shaft 2 is retained by bearings 5 and 6 in a housing madeup only of the housing parts 3 and 4. Pistons 8 are arranged incylindrical bores 7 within the cylindrical drum 1 and are supportedthrough sliding shoes 9 on the swash plate 10. The swash plate 10comprises the cylindrical bearing surface 11 which is situated oppositethe hollow cylindrical bearing surface 12 in the housing part 4. Thestroke of the pistons 8 in the cylindrical bores 7 is varied in a knownmanner by changing the angular position α of the swash plate 10 relativeto the axis 13 of the shaft 2. For effecting this, an adjusting device,not shown, is applied, for example, to a lever, also not shown, that isfirmly connected to the swash plate 10.

The rolling bearing segment 14 shown in FIG. 1, whose rolling elements15 are guided and retained by the cage 16, is arranged in the bearinggap between the bearing surfaces 11 and 12. As can best be seen in FIGS.2, 3, 4 and 5, the cage 16 is connected on the right to the support peg17 which is surrounded on a part of its axial length by the metal ring18. According to FIGS. 3 and 4, this metal ring 18 may comprise aradially inward directed projection 19 so that a positive engagement isformed between the metal ring 18 and the support peg 17. As FIG. 4further shows, the metal ring 18 may also comprise a depression 20extending at least over a part of its outer peripheral surface, intowhich depression 20, the readjusting device can engage if required.Finally, FIG. 5 shows a metal ring whose left-hand inner end face issprayed over with material of the cage.

What is claimed is:
 1. A swash plate pivoting bearing for a hydraulicaxial piston machine in which rolling bearing segments (14) are arrangedbetween a hollow cylindrical bearing surface (12) for the swash plate(10) in a housing (4) and a cylindrical bearing surface (11) on theswash plate (10), which rolling bearing segments (14) are retained inarc-shaped cages (16) that are configured as solid cages and comprise asupport peg (17) for repositioning the cage (16) upon displacement froma desired position, said support peg (17) extending parallel to therolling element pockets and projecting beyond the cage width while beingconnected to a readjusting device, characterized in that the cage (16)and the support peg (17) are made as a single piece out of a polymermaterial, and the support peg (17) is surrounded, at least over a partof its axial length, by a metal ring (18) which comprises a projection(19) on its inner peripheral surface.
 2. A swash plate pivoting bearingaccording to claim 1, characterized in that the metal ring (18) is madeof a steel material and subjected to a heat treatment.
 3. A swash platepivoting bearing according to claim 1, characterized in that the metalring (18) comprises a depression (20) at least on a part of its outerperipheral surface.
 4. A swash plate pivoting bearing according to claim1, characterized in that the metal ring (18) is sprayed over on itsinner end face with cage material.